Radish Yellow Edge Virus, a Seed-borne Virus with Double-stranded RNA, of a Possible New Group

Abstract

Radish yellow edge virus (RYEV) was purified from infected Japanese radish (Raphanus sativus L.) by CsCl equilibrium density gradient centrifugation. Virus particles banded with a buoyant density of about 1.37g/cm³ in CsCl. Purified RYEV preparations showed UV absorption spectrum characteristic of a nucleoprotein with A_max/A_min and A₂₆₀/A₂₈₀ ratios of about 1.10 and 1.39, respectively. Proteins from purified RYEV preparations, electrophoresed in SDS-polyacrylamide gels, migrated as two species with mol. wt. of about 63, 000 and 61, 000. RYEV nucleic acid was judged to be double-stranded ribonucleic acid (dsRNA) from its resistance to RNase in high ionic strength conditions and from its reaction with an antiserum to poly (I): poly (C). In polyacrylamide gel electrophoresis, RYEV dsRNA was fractionated into three major classes with mol. wt. of approximately 1.30, 1.25, 1.21×10⁶ and two minor ones of 1.14, 1.09×10⁶. RYEV was not related serologically to turnip crinkle, turnip rosette, turnip mosaic and cucumber mosaic viruses which infect crucifers or to ten seed-borne viruses which resemble RYEV in particle morphology and biological aspects. It is highly likely that RYEV and several other seed-borne dsRNA viruses constitute a new group of plant viruses.